Here's what I do with monitor sized speakers:
1. Buy the x-large heavy duty trash bags from Home Depot, lay the bag flat and gift wrap the speaker like you would wrap a gift;
2. Buy solid sheets of styrofoam and place several inches of solid styrofoam all around the speaker and buy a box large enough for several inches of styrofoam.
3. With this much solid styrofoam encasing the speaker, one box may be sufficient, but double box it just to be safe
1. Buy the x-large heavy duty trash bags from Home Depot, lay the bag flat and gift wrap the speaker like you would wrap a gift;
2. Buy solid sheets of styrofoam and place several inches of solid styrofoam all around the speaker and buy a box large enough for several inches of styrofoam.
3. With this much solid styrofoam encasing the speaker, one box may be sufficient, but double box it just to be safe